In an image forming apparatus of this type, a scanner device uses laser light to scan each set of data for a sheet from among a number of sheet data sets of image data. As a result, electrostatic latent images are sequentially formed on a photoconductor. A developer then develops these images. An intermediate transfer object sequentially supports the individual developer images, thereby forming a full representation of the image data from the developer image data on the intermediate transfer object. The combined supported developer images are then transferred to a transported sheet, thereby forming a printed image. After which, scanning of the next set of data for a subsequent sheet is immediately started without regard to the success or failure of the printing operation of the previous sheet.
The following patent documents 1 and 2 disclose the detection of a sheet at a predetermined position in order to transfer an image at a location for which the transferred image will not have missing portions (i.e., a loss of an image or a partial image) or without mutual interference from later or earlier images. In addition, the patent documents also disclose the determination of the timing for writing a developer image on the photoconductor.
[Patent Document 1] Japanese Laid-Open Patent No. 08-314232.
[Patent Document 2] Japanese Laid-Open Patent No. 2005-043627.
However, various sizes and types of sheet are loaded into an image forming apparatus. Among these types of sheet, the length of a loaded sheet (with respect to a transport direction) may be relatively short when compared with a nominal or regular size sheet. Additionally, an inappropriately sized sheet may be inadvertently loaded for image forming (e.g., such as the use of A4 size sheet in place of 8½×11 in). In this case, if the image forming is performed without correcting the situation, a part of the image may not appear on the sheet. As a result, only a partial image may be formed on the sheet. These results may not cause significant problems if the image data is received from a peripheral computer or if the image data is obtained by executing the copying function of the apparatus. This is because these operations can be easily repeated after arranging for an appropriately sized sheet.
However, when the image data is remotely transmitted through the communication circuit of a facsimile device, etc., for example, it may become necessary to request that the data source re-transmit the image data. In addition, in the case of a multi-page transmission, subsequent partial images may automatically continue to be output, unless the image forming operation is stopped. This wastes additional sheets.
Particularly, even if an image forming apparatus, provided with the previously identified intermediate transfer device, attempts to stop the image forming operation when an image loss is detected, for example by checking an output sheet, the developer images corresponding to a subsequent set of image data may already be formed on the intermediate transfer device. Therefore, resources are wasted, including developing agent, etc.
The present invention has been completed in consideration of the previously mentioned problems. An objective of this invention is to provide an image forming apparatus capable of preventing wasteful image formation when an image loss occurs.